The present invention relates to a process for preparing polyolefins using a novel polymerization catalyst.
In this technical field, a catalyst comprising a magnesium halide and a transition metal compound such as a titanium compound supported thereon has heretofore been known as described in Japanese Patent Publication No. 12105/1964. Also, a catalyst prepared by the co-pulverization of a magnesium halide and titanium tetrachloride is known from Belgian Pat. No. 742,112.
However, when viewed from the standpoint that the catalytic activity is desired to be as high as possible in the manufacture of polyolefins, the process disclosed in the Japanese Patent Publication No. 12105/1964 is still unsatisfactory because of a low polymerization activity, while the polymerization activity attained in the process of the Belgian Pat. No. 742,112 is fairly high, but a further improvement is desired.
In the process disclosed in German Pat. No. 2137872, the amount of a magnesium halide used is substantially decreased by the co-pulverization thereof with titanium tetrachloride and alumina, but a remarkable increase in activity per solid, which can be regarded as a guideline for productivity, is not recognized, and it is desired to develop a catalyst of a higher activity.
In the manufacture of polyolefins, moreover, it is also desirable from the aspects of productivity and handling that the bulk density of the resulting polymer be as high as possible. From this standpoint, the process disclosed in the Japanese Patent Publication No. 12105/1964 is not satisfactory in both the bulk density of the resulting polymer and polymerization activity, while in the process disclosed in the Belgian Pat. No. 742,112, the polymerization activity is high, but the bulk density of the resulting polymer is low. Thus, in both the processes, a further improvement is desired.